This invention relates to electro-mechanical assemblies of multiple integrated circuit packages (IC packages); and more particularly, it relates to the structure of a heat sink in such an assembly which cools at least two IC packages.
By an IC package is herein meant a thin-flat ceramic or plastic housing which encapsulates one or more integrated circuit chips and has dozens of input/output leads (I/O leads) that extend from the housing. Through these I/O leads, power and signals are sent to/received from each encapsulated chip. Conventionally, multiple IC packages are mounted on a printed circuit board by soldering their I/O leads to corresponding patterned conductors on the board. Also conventionally, multiple printed circuit boards are mounted side-by-side on a backplane which has several parallel spaced apart connectors, one for each printed circuit board.
Since the integrated circuit chips in the IC packages dissipate power, those IC packages get hot. Consequently, some cooling means must be provided to prevent the IC packages from getting overheated. Otherwise, certain maximum operating temperatures of the chips in the IC packages will be exceeded which in turn will cause those IC chips to degrade and/or fail.
Conventionally, the IC packages are cooled by attaching a separate heat sink to each IC package, and by providing one or more fans to blow air past the heat sinks. However, as the amount of power which an IC package uses is increased, the amount of heat which that IC package dissipates also increases. This additional heat can be removed by increasing the size of each sink; but eventually, a point is reached where there is no more room to further increase the heat sink size. On any one printed circuit board, the maximum heat sink width is limited by the distance to the adjacent IC packages, and the maximum heat sink height is limited by the distance to the next printed circuit board.
Alternatively, more fans can be added to blow the air past the heat sinks at a higher speed. However, adding fans increases the cost of the overall system. Further, as the speed of the air is increased, an increased amount of noise occurs due to the moving air, the moving fans, and the fan motors. Thus in a commercial product which needs to operate quietly, such as a desk top computer work station, a practical upper limit for the air speed is soon reached.
Accordingly, a primary object of the present invention is to provide a novel electro-mechanical assembly of multiple IC packages in which the above problems are overcome.